Portable electrocardiograph
A portable electrocardiograph includes a first electrode on an outer surface of a device main body and a second electrode drawn outside the device main body via a connection cable. The first electrode and the second electrode are brought into contact with a body surface. Then, a potential difference between the first and second electrodes is measured in order to measure an electrocardiographic waveform. In this manner, a noise caused by a myoelectric potential produced in muscles other than cardiac muscle is not superposed on the electrocardiographic waveform, and the electrocardiographic waveform can precisely be measured in a stable manner.
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1. Field of the Invention
The present invention relates to a portable electrocardiograph capable of easily measuring and storing electrocardiographic waveforms.
2. Description of the Background Art
Generally, for diagnosing ischemic cardiomyopathies such as angina pectoris and myocardial infarction, an electrocardiogram of a patient is used. Known electrocardiographs used for measuring electrocardiographic waveforms include a stationary electrocardiograph and a portable electrocardiograph.
The stationary electrocardiograph is installed in a medical institution such as a hospital and is used in such a manner that electrodes are attached to a body of a patient who lies on a bed or the like to measure electrocardiographic waveforms. Measurement of the electrocardiographic waveforms by using the stationary electrocardiograph is advantageous in that various electrocardiographic waveforms (such as P waveform, QRS waveform, or ST waveform) can precisely be measured. On the other hand, there is a possibility that an abnormal waveform is not necessarily reproduced at the time of measurement, and a symptom of a patient sometimes cannot properly be observed at the time of diagnosis by a physician.
Portable electrocardiographs are roughly divided into a Holter electrocardiograph for continuously measuring and storing electrocardiographic waveforms while electrodes are attached to the body of the patient who lives daily life for one day to several days, and an event-type electrocardiograph for measuring and storing electrocardiographic waveforms when a subjective symptom to be measured such as palpitation or pant occurs.
In the Holter electrocardiograph, a state where the electrodes are attached to the body of the patient should be maintained for a long time. Accordingly, an adhesion-type electrode is normally adopted as each of a plurality of measurement electrodes. The adhesion-type electrode is implemented by applying a conductive adhesive on a surface of the measurement electrode. The electrode is attached to the body by means of an adhesive layer. It is noted that the adhesion-type electrode is electrically connected to a device main body via a connection cable extending from an electrode body.
In the Holter electrocardiograph, abnormal waveforms can reliably be measured. On the other hand, since the state where electrodes are attached to the patient should be maintained for one day to several days, the patient may feel unpleasant or pain.
Known event-type portable electrocardiographs include an electrocardiograph of a type in which an electrode for measuring electrocardiographic waveforms is always in contact with a prescribed site of the body and an electrocardiograph of a type in which a subject himself/herself contacts an electrode with the body when a subjective symptom to be measured occurs.
In the former event-type portable electrocardiograph, like the Holter portable electrocardiograph, the state where the electrode is always in contact with the body has to be maintained. As such, the adhesion-type electrode is employed. Here, the subject suffers from unpleasant feeling or pain, as in the case of the Holter portable electrocardiograph described above. In contrast, in the latter event-type portable electrocardiograph, the electrode should be brought into contact with the body only when necessary. Therefore, the event-type portable electrocardiograph is very easy to use for the subject.
As the latter event-type portable electrocardiographs, various electrocardiographs structured such that an electrode is provided on an outer surface of the device main body have been proposed.
For example, as shown in
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Meanwhile, in Japanese Patent Laying-Open No. 9-56686 discloses a portable electrocardiograph structured so as to be capable of switching between Holter-type and event-type depending on a purpose of use. As shown in
When this electrocardiograph is used as the event-type electrocardiograph, the adhesion-type electrodes are disconnected from device main body 110. Then, one measurement electrode 121 and indifferent electrode 123 are brought into contact with the body by holding main body portion 193 with the right hand, and the other measurement electrode 122 provided at the tip end of arm portion 194 is pressed against the chest. On the other hand, when the electrocardiograph is used as the Holter-type portable electrocardiograph, connector 182 of connection cables 181 extending from the adhesion-type electrodes is inserted in jack 150 provided in device main body 110 in a direction shown with an arrow D in the drawing, and the adhesion-type electrode is attached to a prescribed site of the chest. In a state where connector 182 is inserted in jack 150, measurement electrodes 121 and 122 as well as indifferent electrode 123 provided on an outer surface of device main body 110 are electrically disconnected from a circuit provided inside the device main body.
In such a portable electrocardiograph as disclosed in each document above, the contact portion between the electrode provided on the outer surface of a housing and the body should be kept stable during a measurement period of several tens of seconds. Unless stable contact is maintained, the measured waveform is disturbed by variation in a contact area between the electrode and the body, and the electrocardiographic waveform cannot precisely be measured in a stable manner.
The conventional portable electrocardiograph described above is intended to maintain contact between the electrode and the body by pressing a hand holding the electrocardiograph main body against abdomen or the like of the body at the time of measurement, and by fixing that hand. More specifically, a wrist, a forearm, an elbow or the like of the holding arm is pressed against the body, thereby preventing the holding hand from being moved during measurement and maintaining stable contact between the electrode and the body. This point will be described in more detailed manner with reference to portable electrocardiograph 100H disclosed in Japanese Patent Laying-Open No. 2003-144403.
In measuring the electrocardiographic waveform in such a measurement posture, if the wrist portion of the right arm is not covered with clothing or the like, the right arm and the right side of the body are in direct contact with each other. Consequently, a measurement circuit (an electric circuit formed in the body from the positive electrode to the negative electrode) is short-circuited in this portion. In such a case, the measurement circuit no longer crosses over the heart, resulting in failure in precise measurement of the electrocardiographic waveform.
Even if the wrist portion of the right arm is covered with clothing or the like, in a state where the portable electrocardiograph is held with the right hand and pressed against the right side of the body, the subject has to put strength in his/her right arm in order to hold the portable electrocardiograph. Here, muscles in the right arm are under a tension, resulting in generation of a myoelectric potential. When the myoelectric potential is produced in the right arm forming a part of the measurement circuit, the myoelectric potential is in turn superposed as noise on the electrocardiographic waveform to be measured. In particular with regard to elderly people who have less flexibility of the body, the myoelectric potential produced when the measurement posture described above is taken is high, which will considerably interfere precise measurement of the electrocardiographic waveform.
A variety of techniques (as disclosed in Japanese Patent Laying-Open Nos. 2000-14653, 2001-346771, 61-206428, and the like) have conventionally been developed in order to solve the above-described problems. The technique disclosed in each document, however, is directed to removal with a filter of noise as result of a myoelectric potential component produced in muscles other than cardiac muscle and mixed in measurement data. Unless complete removal of the noise is achieved, precise electrocardiographic data cannot be obtained. On the other hand, complete removal of the noise is substantially impossible, and it has been extremely difficult to accurately and precisely measure each characteristic waveform in the electrocardiographic waveforms (such as P waveform, QRS waveform, ST waveform, or the like) even with these techniques.
SUMMARY OF THE INVENTIONAn object of the present invention is to provide a portable electrocardiograph capable of precisely measuring an electrocardiographic waveform in a stable manner, without noise caused by a myoelectric potential produced in muscles other than cardiac muscle being superposed on the electrocardiographic waveform.
The inventors have conceived that superposition on the electrocardiographic waveform of the noise caused by the myoelectric potential produced in muscles other than cardiac muscle can be avoided by measuring the electrocardiographic waveform while a measurement posture preventing muscles in the right arm from being under tension is taken, and have found a measurement posture completely different from a posture taken in using a conventional portable electrocardiograph. More specifically, the inventors have found that superposition on the electrocardiographic waveform of the noise caused by the myoelectric potential produced in muscles in the right arm can considerably be suppressed by measuring the electrocardiographic waveform when such a posture that the right arm is supported by some kind of base or such a posture that the subject has his/her right arm vertically hang down is taken, thereby attaining precise measurement of the electrocardiographic waveform in a stable manner. The inventors have studied and developed a portable electrocardiograph allowing such a measurement posture, and finally completed the present invention.
A portable electrocardiograph according to the present invention measures an electrocardiographic waveform by measuring a potential difference produced between a first electrode and a second electrode brought into contact with a body surface. The first electrode is provided on an outer surface of a device main body, and the second electrode is drawn outside the device main body via a connection cable.
Preferably, in the portable electrocardiograph according to the present invention, the device main body has a substantially rectangular parallelepiped shape, and the first electrode is provided on an end surface located at one end in a longitudinal direction of the device main body.
Preferably, the connection cable is attached to the device main body in a detachable manner.
Preferably, in the portable electrocardiograph according to the present invention, the device main body includes wind-up means for winding up the connection cable in the device main body.
Preferably, in the portable electrocardiograph according to the present invention, the device main body includes a storage space accommodating the connection cable and the second electrode.
Preferably, in the portable electrocardiograph according to the present invention, the first electrode is to be brought into contact with a right hand, and the second electrode is to be brought into contact with a chest.
Preferably, in the portable electrocardiograph according to the present invention, the first electrode is to be brought into contact with a chest while the device main body is held with a left hand, and the second electrode is to be brought into contact with a right hand.
According to the present invention, superposition on the electrocardiographic waveform of the noise caused by the myoelectric potential produced in muscles other than cardiac muscle is avoided, thereby allowing precise measurement of the electrocardiographic waveform. Therefore, the present invention contributes to early detection of ischemic cardiomyopathies or the like, and allows proper diagnosis.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following, embodiments of the present invention will be described in detail with reference to the drawings.
First EmbodimentFirst, an overall structure of a portable electrocardiograph 100A in the present embodiment will be described.
As shown in FIGS. 1 to 6, in order to realize excellent usability, portable electrocardiograph 100A in the present embodiment has such a light weight and a small size that it can be held by one hand. Portable electrocardiograph 100A includes a device main body 110 and an external electrode unit 160A.
A structure of device main body 110 will now be described. Device main body 110 has a flat and elongated, substantially rectangular parallelepiped shape. On its outer surfaces (front face 111, rear face 112, top face 113, bottom face 114, right side face 115, and left side face 116), a display unit, an operation unit, electrodes and the like are disposed.
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First electrode 121 and indifferent electrode 123 described above are formed with a conductive member, and electrically connected to a circuit formed inside device main body 110. In addition, first electrode 121 and indifferent electrode 123 are disposed in concave portion 115a provided in right side face 115 such that their surfaces are exposed on the outer surface of device main body 110. The first electrode 121 is located closer to top face 113 on right side face 115, while indifferent electrode 123 is located closer to bottom face 114 on right side face 115.
As shown in
A structure of external electrode unit 160A will now be described. As shown in
Connection cable 181 has one end electrically connected to second electrode 122, and has the other end connected to connector 182. Preferably, a highly flexible connection cable 181 is used, from the viewpoint of ease of use. Connector 182 is detachably inserted in jack 150 provided in device main body 110 described above. When connector 182 is inserted in jack 150, second electrode 122 provided in external electrode unit 160A is electrically connected to the circuit provided inside device main body 110.
Next, a measurement posture to be taken by the subject in measuring an electrocardiographic waveform using portable electrocardiograph 100A having the above-described structure will be described.
As shown in
Then, the subject holds a portion closer to one end in the longitudinal direction of device main body 110 such that right side face 115 of device main body 110 is covered with forefinger 212 of right hand 210. Right forearm 220 is placed on a base such as a desk 300. Here, subject 200 preferably sits on a chair or the like, and takes a relaxed posture without imposing burden on the body.
Thereafter, attachment portion 171 of external electrode unit 160A is stuck to chest 250. More specifically, attachment portion 171 is stuck such that second electrode 122 provided in external electrode unit 160A comes in contact with the skin on a fifth intercostal anterior axillary line of chest 250. Then, the subject presses measurement button 142 provided on front face 111 of device main body 110 with his/her thumb 211 of right hand 210 holding device main body 110, and maintains the measurement posture at ease for several tens of seconds until measurement of the electrocardiographic waveform is completed.
A state that portable electrocardiograph 100A is held with right hand 210 will now be described.
As shown in
In this state, forefinger 212 of right hand 210 is lightly bent such that the forefinger extends along curved right side face 115 and is inserted in concave portion 115a provided in right side face 115. Forefinger 212 of right hand 210 is thus brought into contact with first electrode 121 and indifferent electrode 123 provided in concave portion 115a.
When such a measurement posture is taken, first electrode 121 and indifferent electrode 123 provided on the outer surface of device main body 110 of portable electrocardiograph 100A come in contact with forefinger 212 of right hand 210 of subject 200, and second electrode 122 connected to device main body 110 via connection cable 181 comes in contact with chest 250 of subject 200. In this manner, a measurement circuit is implemented by right hand 210 being in contact with first electrode 121, forearm 220 without contacting chest 250, a brachium 230 and a right shoulder 240 without contacting chest 250, and chest 250 to which second electrode 122 is attached, in this order.
According to portable electrocardiograph 100A in the present embodiment, a potential difference produced between first electrode 121 provided on the outer surface of device main body 110 and second electrode 122 drawn outside device main body 110 via connection cable 181 is measured, so as to measure the electrocardiographic waveform. With such a structure, the measurement posture as shown in
In the measurement posture shown in
In addition, according to portable electrocardiograph 100A in the present embodiment, first electrode 121 provided on the outer surface of device main body 110 is provided on right side face 115 located at one end in the longitudinal direction of device main body 110. Accordingly, when the electrocardiographic waveform is measured while the measurement posture as shown in
Moreover, according to portable electrocardiograph 100A in the present embodiment, external electrode unit 160A including connection cable 181 is attached to device main body 110 in a detachable manner, thereby portability being improved.
Though the external electrode unit including the adhesion-type electrode has been described by way of example in the present embodiment, the external electrode unit connected to the device main body is not necessarily limited to the above-described type. For example, an external electrode unit including a suction-cup-type electrode or an external electrode unit including a pressed-type electrode may be adopted.
An external electrode unit 160B shown in
In attaching the suction-cup-type electrode to the body, negative pressure creating portion 172 is pinched by fingers, so as to compress an internal space. Then, suction cup portion 173 is pressed against a prescribed site of the body, and the fingers that have been pinched negative pressure creating portion 172 are removed. Then, a negative pressure is caused in the internal space, and the suction-cup-type electrode is stuck and held to the body. When the external electrode unit including such a suction-cup-type electrode is employed as well, the electrocardiographic waveform can precisely be measured in a stable manner, as in employing the external electrode unit including the adhesion-type electrode.
An external electrode unit 160C shown in
In bringing the pressed-type electrode into contact with the body, base body 174 is held with a left hand and pressed against a prescribed site of the body. When the external electrode unit including such a pressed-type electrode is employed as well, the electrocardiographic waveform can precisely be measured in a stable manner, as in employing the external electrode unit including the adhesion-type electrode.
Second EmbodimentAn overall structure of a portable electrocardiograph 100B in the present embodiment will now be described.
As shown in FIGS. 12 to 17, in order to realize excellent usability, portable electrocardiograph 100B in the present embodiment has such a light weight and a small size that it can be held by one hand, as in the portable electrocardiograph in the first embodiment described above. Portable electrocardiograph 100B includes device main body 110 and an external electrode unit 160D.
A structure of device main body 110 will now be described. Device main body 110 has a flat and elongated, substantially rectangular parallelepiped shape. On its outer surfaces (front face 111, rear face 112, top face 113, bottom face 114, right side face 115, and left side face 116), a display unit, an operation unit, electrodes and the like are disposed.
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Left side face 116 has a smoothly curved shape, such that a forefinger of the left hand of the subject is fitted thereto when the subject takes a measurement posture which will be described later. In addition, a concave portion 116a extending in an up-down direction is formed in left side face 116. Concave portion 116a is in a shape to receive the forefinger of the left hand of the subject.
A structure of external electrode unit 160D will now be described. As shown in
Connection cable 181 has one end electrically connected to second electrode 122, and has the other end connected to connector 182. Preferably, a highly flexible connection cable 181 is used, from the viewpoint of ease of use. Connector 182 is detachably inserted in jack 150 provided in device main body 110 described above. When connector 182 is inserted in jack 150, second electrode 122 provided in external electrode unit 160D is electrically connected to the circuit provided inside device main body 110.
Next, a measurement posture to be taken by the subject in measuring an electrocardiographic waveform using portable electrocardiograph 100B having the above-described structure will be described.
As shown in
Then, forefinger 212 of right hand 210 is inserted in the inner space of base body 175 of external electrode unit 160D, so as to bring forefinger 212 into contact with second electrode 122. Right forearm 220 is placed on the base such as desk 300. Here, preferably, thumb 211 of right hand 210 is brought into contact with a rear face of base body 175. In this manner, base body 175 is held by forefinger 212 and thumb 211 in a stable manner, and contact between second electrode 122 and forefinger 212 of right hand 210 is maintained in a stable manner.
Then, the subject holds a portion closer to the other end in the longitudinal direction of device main body 110 such that left side face 116 of device main body 110 is covered with a forefinger 262 of a left hand 260, and first electrode 121 provided on right side face 115 of device main body 110 is brought in direct contact with the skin on the fifth intercostal anterior axillary line located in a lower left portion of chest 250. Here, subject 200 preferably sits on a chair or the like, and takes a relaxed posture without imposing burden on the body. Then, the subject presses measurement button 142 provided on front face 111 of device main body 110 with a thumb 261 of left hand 260 holding device main body 110, and the subject maintains this measurement posture at ease for several tens of seconds until measurement of the electrocardiographic waveform is completed.
A state that portable electrocardiograph 100B is held with left hand 260 will now be described.
As shown in
In this state, forefinger 262 of left hand 260 is lightly bent such that the forefinger extends along curved left side face 116 and is inserted in concave portion 116a provided in left side face 116. Forefinger 262 of left hand 260 is thus brought into contact with indifferent electrode 123 provided in concave portion 116a.
When such a measurement posture is taken, first electrode 121 provided on right side face 115 of device main body 110 of portable electrocardiograph 100B comes in contact with chest 250 of subject 200, and indifferent electrode 123 provided on left side face 116 of device main body 110 comes in contact with forefinger 262 of left hand 260 of subject 200. In addition, second electrode 122 connected to device main body 110 via connection cable 181 comes in contact with forefinger 212 of right hand 210 of subject 200. In this manner, a measurement circuit is implemented by right hand 210 being in contact with second electrode 122, forearm 220 without contacting chest 250, brachium 230 and right shoulder 240 without contacting chest 250, and chest 250 to which first electrode 121 is attached, in this order.
According to portable electrocardiograph 100B in the present embodiment, a potential difference produced between first electrode 121 provided on the outer surface of device main body 110 and second electrode 122 drawn outside device main body 110 via connection cable 181 is measured, so as to measure the electrocardiographic waveform. With such a structure, the measurement posture as shown in
In the measurement posture shown in
In addition, according to portable electrocardiograph 100B in the present embodiment, first electrode 121 provided on the outer surface of device main body 110 is provided on right side face 115 located at one end in the longitudinal direction of device main body 110. Accordingly, the measurement posture to allow the measurement circuit to cross over the heart is realized in an ensured manner, and short-circuit of the measurement circuit due to contact of right hand 210, forearm 220 and brachium 230 with chest 250 is prevented. When the electrocardiographic waveform is measured while the measurement posture as shown in
Moreover, according to portable electrocardiograph 100B in the present embodiment, external electrode unit 160D including connection cable 181 is attached to device main body 110 in a detachable manner, thereby portability being improved.
Though the external electrode unit including the electrode receiving the right forefinger has been described by way of example in the present embodiment, the external electrode unit connected to the device main body is not necessarily limited to the above-described type. For example, an external electrode unit including a grip-type electrode or an external electrode unit including a pinched-type electrode may be adopted. In addition, though portable electrocardiograph 100B in the present embodiment has indifferent electrode 123 disposed on left side face 116 of device main body 110, indifferent electrode 123 may be provided in the external electrode unit instead of being disposed on device main body 110, as will be described later.
An external electrode unit 160E shown in
In contacting the grip-type electrode with the body, base body 176 is gripped by the right hand. During measurement, attention should be paid not to release the hand. When the external electrode unit including such a grip-type electrode is employed as well, the electrocardiographic waveform can precisely be measured in a stable manner.
An external electrode unit 160F shown in
In contacting the pinched-type electrode with the body, for example, the thumb of the right hand is brought into contact with indifferent electrode 123, the forefinger and the middle finger of the right hand are brought into contact with second electrode 122. In doing so, base body 177 is held with the right hand, and attention should be paid not to release the hand during measurement. When the external electrode unit including such a pinched-type electrode is employed as well, the electrocardiographic waveform can precisely be measured in a stable manner.
Portable electrocardiograph 100B in the present embodiment may adopt external electrode unit 160A including what is called the adhesion-type electrode described in the first embodiment above.
As shown in
A portable electrocardiograph 100C in the present embodiment is intended to measure the electrocardiographic waveform in the measurement posture shown in
As shown in
According to such a structure, not only the length of connection cable 181 can be adjusted, but also connection cable 181 is wound by means of cord reel 158 during a period in which measurement is not performed. Accordingly, a portable electrocardiograph attaining excellent portability can be obtained.
As shown in
A portable electrocardiograph 100D in the present embodiment is intended to measure the electrocardiographic waveform in the measurement posture shown in
As shown in
Connection cable 181 is directly drawn out from device main body 110, and has its tip end connected to connector 182. Connector 182 is inserted in a jack 171a provided in attachment portion 171 of the adhesion-type electrode, so as to be electrically connected to second electrode 122.
According to such a structure, connection cable 181 can be stored inside device main body 110 during a period in which measurement is not performed. Accordingly, a portable electrocardiograph attaining excellent portability can be obtained. In order to achieve further improvement in portability, a storage space for accommodating the adhesion-type electrode may be provided within device main body 110.
Though embodiments based on the present invention have been described above, the present invention is not limited to those embodiments. The present invention aims to provide one electrode out of the measurement electrodes in the device main body of the portable electrocardiograph and the other electrode in a manner drawn outside the device main body, in order to adopt a measurement posture without putting unnecessary strength into the right arm for the purpose of suppressing generation of a myoelectric potential produced in muscles in the right arm during measurement of an electrocardiographic waveform. Therefore, a structure other than those can be modified as appropriate. For example, a position where an indifferent electrode is disposed or a position where a display unit, an operation unit, or the like is disposed can be modified as appropriate.
With regard to a position where the electrode is attached to the body, it is preferable to attach the electrode to the position described in the embodiments above, considering the purpose of precisely measuring an electrocardiographic waveform in a stable manner. Measurement, however, can be performed also when the electrode is attached to a different position.
Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.
Claims
1. A portable electrocardiograph measuring an electrocardiographic waveform by measuring a potential difference produced between a first electrode and a second electrode being in contact with a body surface, wherein
- said first electrode is provided on an outer surface of a device main body, and
- said second electrode is drawn outside said device main body via a connection cable.
2. The portable electrocardiograph according to claim 1, wherein
- said device main body has a substantially rectangular parallelepiped shape, and
- said first electrode is provided on an end surface located at one end in a longitudinal direction of said device main body.
3. The portable electrocardiograph according to claim 2, wherein
- said first electrode is to be brought into contact with a right hand, and
- said second electrode is to be brought into contact with a chest.
4. The portable electrocardiograph according to claim 2, wherein
- said first electrode is to be brought into contact with a chest while said device main body is held with a left hand, and
- said second electrode is to be brought into contact with a right hand.
5. The portable electrocardiograph according to claim 1, wherein
- said connection cable is attached to said device main body in a detachable manner.
6. The portable electrocardiograph according to claim 1, wherein
- said device main body includes wind-up means for winding up said connection cable in said device main body.
7. The portable electrocardiograph according to claim 1, wherein
- said device main body includes a storage space accommodating said connection cable and said second electrode.
8. The portable electrocardiograph according to claim 1, wherein
- said first electrode is to be brought into contact with a right hand, and
- said second electrode is to be brought into contact with a chest.
9. The portable electrocardiograph according to claim 1, wherein
- said first electrode is to be brought into contact with a chest while said device main body is held with a left hand, and
- said second electrode is to be brought into contact with a right hand.
Type: Application
Filed: Dec 27, 2004
Publication Date: Jun 30, 2005
Applicant: OMRON HEALTHCARE CO., LTD. (Kyoto-shi)
Inventors: Masahiro Umeda (Kyoto-shi), Norihito Yamamoto (Otsu-shi), Junichi Ishida (Kyoto-shi), Kazuhisa Tanabe (Kyoto-shi), Yoko Moroki (Kyoto-shi)
Application Number: 11/020,322